//1.ts类型:boolean类型
let bo: boolean = true
bo=false

//2.ts类型:number类型
let nu: number = 1
nu=2

//3.ts类型:string
let st: string = '1'
st = '2'

//4.ts类型:null和undefined
let n: null = null
let u: undefined = undefined

//ts类型:bigint(编译时可能报错,因为是es2020的规范,ts默认配置的支持范围小于es2020)
let nu2: bigint = 1n

//ts类型:symbol
let sy1: symbol = Symbol()
